I9S 



NA TURE 



[June 27. 1895 



there is no apparent reason why it should cease its ravages 

 before it has entirely destroyed its particular host. It is 

 fortunate for agriculturists that the great increase of any 

 particular parasite seems ultimately to work out its own 

 destruction ; and frequently when all hope seems over, the 

 plague rapidly and unaccountably disappears. 



Surprise has been expressed that ticks infesting cattle 

 have received so little real study. Quite recently the 

 statement appeared that these parasites formed the least 

 known part of the tropical fauna. But a great deal has 

 been done in this direction of recent years, and there 

 seems some hope of real progress being made. 



Taking the conditions into consideration, it is a matter of 

 great wonder that so few ticks exist in many parts of the 

 tropics. No real attempt has been made to decrease their 

 numbers, and there appears to be no season of the year 

 when the climate is fatal to them. \'egetation is rank, 

 and we know now that they can li\e to a great extent upon 

 vegetable matter ; further, c\en where there is a scarcity 

 of small indigenous mammals, there are plenty of horses 

 and cattle. The multiplying powers of ticks arc enormous. 

 In one case I detennined the number of eggs from one 

 female as over 20,000 (see Fig. 3), and almost all of these 

 were fertile and produced young ticks. The increase in 

 numbers of ticks in most countries is not marked, however, 

 and we are driven to the conclusion that there is here, in 

 the animal kingdom, a waste of material analogous to that 

 in the seeding of parasites and saprophytes amony plants. 



It is not surprising now and then to hear of a long- 

 continued plague of ticks from one place or another where 

 cattle-rearing is a staple industr)-. In Jamaica, it is by no 

 means uncommon for the traveller to get covered with 

 " grass-lice." On pushing aside the branches overhang- 

 ing the riding path, 1 have been immediately covered with 

 firmly attached young ticks which needed much care and 

 patience to remove. The ticks of Jamaica are now a ver^' 

 serious source of anxiety in cattle-pens, and much loss is 

 attributed to these parasites. 



During my stay in .•\ntigua, complaints were loud and 

 frequent of the ravages of a large tick, which infested 

 the cattle between the months of May and September. 

 In the cattle and sheep farms of the Cape of (lood Hope 

 and .\ustralia the "tick" matter is absorbing much atten- 

 tion. Specially large and annoying forms arc described 

 from parts of India, Central Africa and Central .•\merica ; 

 while extraordin.ar)' tales are told of the destruction caused 

 by these par.isitcs in cattle-rearing districts of South 

 America. Elaborate and expensive researches have been 

 conducted in the United States Southern Experimental 

 Stations upon the lifc-histor)' of the ticks and their re- 

 lations to cattle ; and the exhaustive reports, issued from 

 the Bureau of .Animal lndustr\', form by far the most 

 valuable part of our economic literature on these pests. 



The books of travellers teem with references to the 

 annoyance caused by ticks. .Sir Joseph Hooker, in his 

 " Himalayan Journals," describes their abundance in the 

 frontier regions between .Sikkim and Nepaul, in pathless 

 tracts destitute of animal life. He writes the following 

 concerning the neighbourhood of Tonglo : " .V large tick 

 infests the small bamboo, and a more hateful insect I 

 never encountered. The traveller cannot avoid these 

 insects coming on his person (sometimes in great numbers) 

 as he brushes through the forest ; they get inside his 

 dress, and insert the proboscis deeply without pain. 

 Buried head and shoulders, and retained by a barbed 

 lancet, the lick is only to be extracted by force which 

 is ver>' painful. I have devised many tortures, mechanical 

 and chemical, to induce these disgusting intruders to 

 withdraw their proboscis, but in vain." 



Bates, on passing through the grassy lanes of the 

 second-growth woods on the Amazons, often found him- 

 self covered by ticks. It occupied him, he says, a full 

 hour after his day's work to clear himself of the parasites. 

 Belt refers to the "grass-lice" on the plains of 



NO. 1339, VOL. 52] 



Nicaragua, as quickly covering anyone travelling throuyh 

 the country- ; so much so, that the herdsmen or " vac- 

 queros" keep a ball of soft wax with which to rub 

 themselves. The smaller ticks are thus removed from 

 their skin, while the larger ones are picked off by hand. 



Many a time, in walking through grass in the Leeward 

 Islands, 1 have been conscious of the peculiar itching 

 at the ankles caused by the attacks of " bete rouge.' 

 The bete rouge is not in reality a tick, although often 

 confused with it. Horses seem to be particularly liable 

 to its attacks, with the result that they lose all the hair 

 about the face and eyes. In all probability the poor 

 animals suffer a good deal, for the personal irritation is- 

 extreme. The bete rouge is exceedingly minute, and, 

 as its name implies, is of a brilliant scarlet. At night, 

 after retiring to rest, the warmth of the body seems to- 

 increase the irritation to the utmost pitch, and sleep 

 becomes .ibsolutcly impossible. Rubbing or scratching 

 the parts attacked merely intensifies the discomfort, the 

 creature pushing itself deeper into the flesh. Most pain- 

 ful sores are the result if the greatest care is not taken. 

 The one certain remedy seems to be to anoint the inflamed 

 spots with vaseline. This substance not only soothes, 

 but appears to destroy the bete rouge by stopjiioi; up its 

 breathing pores. 1 have never succeeded in detecting the- 

 creature on the skin, but, when reailing in or near an 

 infested lawn, I have captured many by watching for the 

 minute scarlet dots travelling over the white paper. 



The damage done by ticks to cattle is undoubtedly 

 very serious. According to observ.ations by Leidy, the 

 adult female tick is able to absorb 100 times its weight 

 of blood, swelling during that time to an enormous ex-- 

 tent. This food is rapidly changed into eggs. The 

 ,idult male does not increase apprecial)ly in size, but 

 his demands upon the host have probably been greatly 

 underrated. .\n account of tick-infested cattle in Queens- 

 land states that they were so completely co\ered that 

 the branding-iron had to be burnt through the ticks 

 before it was possible to reach the animals' skins. A 

 case in Texas is mentioned where it was found impossible 

 to lay a silver dollar upon the body of the animals with- 

 out touching some ticks, .\gain in Texas, 100 full-grown 

 ticks were collected from each ear of a pony, while many 

 immature ones were left behind. The mere abstraction 

 of blood must, in this case, be a very serious drain upon 

 the system. 



When one considers, further, the irritation experienced 

 by travellers from the few ticks fixed upon them in their 

 daily rambles, it may be safely concluded that the pene- 

 tration of the countless proboscides into the skin of cattle 

 must of itself be a source of great discomfort, especially 

 as these animals are quite unable to get rid of them. 

 Calves not uncommonly are destroyed by the formation 

 of balls ofliair in their stomachs ; and in tick-regions this 

 is undoubtedly due to an attemi)t to f^et rid of tlie parasites 

 by licking and biting them off. 



It is quite conceivable, then, that ticks do really cause 

 the death of multitudes o( cattle on the great estates 

 where it is impossible to examine them closely. We 

 should, however, approach this part of the subject with 

 caution. Sickly cattle are usually covered by ticks, while 

 the healthy ones have only a few ; but it is questionable 

 whether the ticks are the real cause of their emaciation. 

 The case of ticks seems rather to be analogous to th.tt 

 of scale insects on plants. The latter pests appear in 

 great quantities at any period of stress, when from lack 

 of nutriment or other cause the plants become weakly. 

 Thus, in .-\ntigua, there is a marked disappearance of 

 scale insects with the commencement of the rainy season. 

 It seems probable that the prevalence of ticks upon 

 certain cattle is rather due to conditions of the blood 

 or skin of the animal, closely connected with its general 

 nutrition. This is an exceedint;ly important matter for 

 determination, for upon it, as will presently be shown. 



